1. Field of the Invention
The present invention relates to apparatus used for observing an object such as the eye fundus or for taking a picture of it while illuminating the object with artificial light, and also relates to apparatus in which magnification for observing or photographing is variable.
2. Description of the Prior Art
Recently, a great emphasis has been placed on the prevention against diseases of adults and examination of the eye has been increasingly conducted for this purpose. A photo-picture of the fundus of the eye gives useful information for diagnosis of diseases of adults. For this reason, there is an increasing tendency to carry out photographing of fundus of the eye in a group. As a reflection of this tendency, it has been desired to provide a such fundus camera of wide picture angle with which a broader area of the fundus can be photographed a smaller number of times. On the other hand, it is also desired to provide a fundus camera which allows photography of the fundus with a narrow picture angle and in a higher magnifying power for the purpose of close examination of those eyes in which some morbid changes have been found at the time of a group examination.
However, it is very difficult to successfully take an enlarged picture of an object while maintaining the size of film or the area of finder visual field unchanged. Due to shortage of quantity of light, the film is insufficiently exposed to light. Also, the visual field becomes too dark to observe the object.